In general, the pleasing color effects which can be obtained in a fabric through the use of what is commonly referred to as "space dyeing" have been recognized in the art. It is also often desirable to dye yarn used in making textile materials to a uniform color. Furthermore, methods and apparatus have been developed over the years to achieve such effects by selectively dyeing portions of a yarn package. As used herein, the term "yarn in package form" or "yarn package" is intended to denote and mean a mass of yarn which has been wound on a core such as a tube, cone, pern dye spring or other such conventional holders and would include also such yarn packages from which the core has been removed. Space dyeing methods fall into two broad categories. One of these categories involves the use of needles to inject dye into selective portions of the yarn package. Typical of this type of treatment is the process disclosed in U.S. Pat. No. 3,547,575. Such prior art methods are time consuming and present problems with reproductibility and uniformity of dyeing. Furthermore, when using fine denier yarns, the needles usually tear the yarn fibers causing obvious problems when the yarn is subsequently fashioned into a fabric by weaving or knitting.
The second broad category of prior art processes is typified by U.S. Pat. No. 3,145,398 in which dye is forced radially through selective portions of a yarn package through the use of centrifugal force. The centrifugal force method exhibits the inherent disadvantage of distorting the yarn package during the process.
It is noted in passing that pressure per se has been used in the prior art for dyeing yarn in package form. However, in such prior art processes, as disclosed for example in U.S. Pat. Nos. 3,878,575 and 1,841,024 the entire package was uniformly dyed to the same shade or color.
Although it is sometimes desirable to uniformly dye a yarn package, these prior art dyeing processes usually involve waste of dye material and energy, which often results in waste treatment and pollution problems. Recirculation of the dye through the yarn package in order to produce a uniform color, as used for example in German Pat. No. 693,409, of necessity is restricted to a single process which produces a single dye effect in the end product. Furthermore, such processes frequently require long periods of time in the order of an hour or more to completely dye a yarn package.
Space dyeing has also been accomplished through the use of resists which alter dye sites in the yarn to cause them to be unreceptive to certain kinds of dyes. See, for example, U.S. Pat. No. 3,743,477 which discloses certain fiber-reactive compounds which may be applied to specified fibers to provide local reservation against dyeing with anionic or acid dyes. See also the application of resists by roller printing to form a pattern of resist and non-resist sections as disclosed in U.S. Pat. No. 3,700,402. However, roller printing fine denier yarns is both impractical and commercially unattractive because of the high cost.
Each of the prior art methods of achieving a varigated dye effect on yarn has one or more undesirable characteristics which has heretofore limited the commercial acceptance of these methods. The need for a new technique which provides the desired pleasing multi-colored or ombre effect, and also provides the capability of uniform dyeing, without undesirable features, is evident. The invention herein is an improvement of the apparatus and method disclosed in U.S. Pat. Nos. 4,165,623 and 4,097,232.